The present invention relates generally to communication networks, and more specifically, to inter-ring protection for shared packet rings.
Spanning-Tree Protocol (STP) is a Layer 2 protocol designed to run on bridges and switches. The STP specification is defined in IEEE 802.1d. The main goal of STP is to make sure that a loop situation does not occur when there are redundant paths in a network. STP accomplishes this by disabling network loops and providing backup links between switches or bridges. STP allows devices to interact with other STP compliant devices in the network to ensure that only one path exists between any two stations on the network. If STP or a similar protocol is not present in a redundant topology network, switches may endlessly flood broadcast packets to all ports (i.e., broadcast storm). When multiple copies of a frame arrive at different ports of a switch, MAC entry instability in a Filtering Database may occur.
STP, RSTP (Rapid Spanning Tree Protocol) (defined in IEEE 802.1W), and other topology discovery protocols provide interconnection of two shared packet rings, however, they do not always provide sub-second convergence during failure.
There is, therefore, a need for a mechanism to interconnect two shared packet rings with redundant interconnect nodes which provide optimal bandwidth across rings and sub-second recovery for link or node failures.